Wireless communications devices, including wireless memory devices for storing and retrieving data such as radio frequency identification ("RFID") tags, are generally known in the art. RFID tags available from a number of manufacturers, including Texas Instruments of Dallas, Tex. and Omron of Japan. Such devices typically employ an antenna coupled to an integrated circuit to transmit and/or receive data in the form of signal in some range of the electromagnetic spectrum.
Antenna structures typically employ an active antenna element driven by a transmitter to transmit data in an outgoing signal and/or driven by an external signal from an external source to receive incoming data. Antenna structures may further employ parasitic or passive antenna elements that electromagnetically cooperate with the driven antenna element to enhance the transmission or reception of the signal. The parasitic antenna elements typically include an array of directors and reflectors, the directors being generally shorter, and the reflectors being generally longer, than the driven element. The parasitic antenna elements are normally aligned with and are carefully spaced from the driven antenna element, and one another, typically at a distance of approximately one-quarter of a wave length corresponding to an operating frequency of the antenna. The parasitic antenna elements are also usually tapered to further enhance the signal transmission and/or reception. One common example of such an antenna structure is the Yagi antenna.
The manufacturing of memory devices, such as RFID tags, typically includes forming an antenna structure and electrical connections such as conductive traces and pads on a circuit substrate. the traces and pads coupling an electronic structure such as an integrated circuit to the antenna. The electronic structure typically includes a memory portion and a logic portion. The logic portion controls the reading, writing, or manipulating of data in the memory portion. The logic portion further couples the memory portion to an antenna to form a transmitter, receiver, or transceiver for reading and/or writing data to, or from, the RFID tag. Thus, for example, an RFID tag may receive and transmit RF signals to write data to the memory and to read data from the memory. The antenna typically consists of either a dipole antenna or a coil or loop antenna formed as a single conductive trace on the surface of the substrate.
The substrate can optionally be laminated between a face sheet and a pressure sensitive adhesive covered by a release liner. The optional face sheet can provide a protective layer over one surface of the circuit substrate, thereby protecting the antenna and electronic structure. The optional release liner can provide a selectively removable protective layer over the pressure sensitive adhesive, which a user removes before affixing the RFID tag to an item or container by way of the adhesive.
The existing laminate structures and methods of manufacturing wireless communications devices present certain problems. The manufacturing of such devices presents particular problems due to their typically narrow dimensions. The range of these devices is also typically limited due to their narrow dimensions. Due to the typically thin profile of most memory tags, the antenna is usually positioned extremely close to the item or container to which the memory device is affixed. This antenna placement unfavorably interferes with good communications from the memory device, especially when the underlying container is made of metal. This antenna placement also reduces the overall range of the memory device. Additionally, the current antenna structures do not take advantage of the signal enhancement that is possible using multiple antenna elements, such as directors and reflectors in a Yagi antenna configuration.
While it is possible to build a relatively high profile memory device that spaces the antenna further away from the package or item than current memory devices, such a high profile device leads to other problems. For example, RFID tags may carry printed indicia such as text or a machine readable symbol. The indicia may be printed on the RFID tag by the end user, after the device has been manufactured. Printing on a relatively high profile device would be extremely difficult and would require specialized equipment, if possible at all.